It is well known in the art to produce photoresist compositions such as those described in U.S. Pat. Nos. 3,666,473, 4,115,128 and 4,173,470. These include phenol-formaldehyde novolak resins together with light-sensitive materials, usually a substituted naphthoquinone diazo compound.
The novolak resin component of those photoresist compositions is soluble in an alkaline aqueous solution, but the naphthoquinone diazo compound acts as a dissolution rate inhibitor with respect to the resin. Upon exposure of selected areas of the coated substrate to actinic radiation, however, the photoresist undergoes a radiation induced structural transformation and the exposed areas of the coating are rendered more soluble than the unexposed areas. The relief pattern of photoresist on substrate prepared by the process mentioned above is useful for providing 1 μm very small line and space widths, for example, in the manufacture of a semiconductor.
Further, in the process for preparing such very small circuits, the circuit density can be increased, using photolithography techniques, by increasing the resolution capabilities of the resist. Such photoresist has been widely used for preparing a semiconductor and a liquid crystal display device. In the liquid crystal display device, examples of using a photosensitive material during color filter process are described in more detail below.
In the color filter process, a positive photosensitive material or a negative photosensitive material containing pigment was coated on the glass or conductive metal film or layer having a rectangular pattern (hereinafter referred to as “substrate”), soft-baked, exposed and developed to prepare a pattern of the desired shape. In the course of forming such fine circuit pattern, when forming a photosensitive film on the substrate, the photoresist film formed at the edge of the substrate becomes irregular when compared with the photoresist film formed at the middle of the substrate. Further, the photosensitive material coated irregularly at the edge of the substrate during soft-baking or exposing process may lead to contamination by an accumulation of photosensitive material and thus, the removal thereof is required.
As the process for removing the coated photoresist layer by a physical process, a process for scraping the layer is known. However, such process has a problem in that the removal of the layer is not regular and the layer is damaged. As the process for stripping and cleaning the photoresist layer by a chemical process, the process for removing the photoresist layer with a chemical solution is known.
U.S. Pat. No. 4,983,490 discloses a solution for treating a photoresist film which comprises from 1 to 10 parts by weight of propylene glycol alkylether (PGME) and from 1 to 10 parts by weight of propylene glycol alkyl ether acetate (PGMEA), which exhibits excellent properties mainly in treating a positive photoresist, but it has disadvantages in treating a negative photoresist. The negative photoresist containing pigment is a photoresist used for a color filter of liquid crystal display devices. As such photoresist, black, red, blue and green photoresists may be used. When the photoresist containing pigment is cleaned with the cleaning composition consisting of from 1 to 10 parts by weight of PGME and from 1 to 10 parts by weight of PGMEA, the cleaning capability is lowered and a residue of the photoresist remains on the boundary surface between the cleaned area and the not-cleaned area of the developer after developing process.